This invention relates to personal care products and particularly to tampons having high fluid absorbent capacity and yet do not cause the vaginal epithelial tissue to dry. This invention also relates to methods of constructing such tampons.
Those familiar with the art of making and using internal vaginal tampons have long been aware that the use of these tampons can cause drying of vaginal epithelial tissue. Drying may cause many irritating vaginal conditions and may lead to discomfort and infection, affecting the health of the tampon wearer.
Although women appreciate that the use of vaginal tampons during menstruation is convenient and discreet, they have found many disadvantages and inconveniences attendant upon tampon use. For example, tampons may unexpectedly leak if they do not expand fully to fill the vaginal canal. The tampons may also become saturated with menstrual fluid unbeknownst to the wearer and begin to leak. Tampons are sometimes hard to insert into or remove from the vaginal canal. The tampons"" absorbent cores sometimes slough off, leaving absorbent fibers in the vagina.
There have been many attempts to remedy these problems by manipulating elements of the tampon""s absorbent core and overwrap.
U.S. Pat. Nos. 2,710,007, (Greiner, et al.) and 3,340,874 (Burgeni) are examples of the use of low density material in portions of a tampon plug in order to promote rapid absorption of fluid.
Some references describe the use of one or two hydrophobic covers to protect the inner core fibers from sloughing and/or to improve the tampon""s lubricity on insertion and withdrawal without reducing the speed of fluid uptake. For example, U.S. Pat. No. 3,055,369 (Graham) and U.S. Pat. No. 3,683,912 (Olson, et al.) describe tampons having an overwrap or sheath of nylon, Orlon, Saran, Dacron or polypropylene.
U.S. Pat. No. 3,815,601 (Schaefer) describes a tampon containing a body of pieces of foam encased in a fine mesh tubular overwrap made of a nonwoven fabric of cotton-rayon or polyester. The overwrap is doubled over on itself. The hydrophobic overwrap is intended to insulate the vaginal wall from collected menses.
U.S. Pat. No. 3,994,298, to Des Marais, describes a tampon with improved wet expansion characteristics, composed of a lubricated foam material treated with a nonionic surfactant. The foam is contained in a fluid permeable overwrap such as that described in Schaefer.
U.S. Pat. No. 3,976,075, (Chinai, et al.) describes an absorbent pad covered, at least on one surface, with a non-occlusive pattern (5% to 75% of the surface area) of an adhesive binder, which serves to prevent sloughing and telescoping of the absorbent pad without decreasing absorptivity.
U.S. Pat. No. 4,239,043 (Gellert) describes a tampon made of blocks of hydrophilic polyester foam or foam-fiber composites in an elongated closed-end fluid permeable sheet material of hydrophilic, hydrophobic or partially hydrophobic polymer such as polyester.
U.S. Pat. No. 4,305,391 (Jackson) describes a tampon composed of a superabsorbent-containing core and two fluid permeable, hydrophobic wraps that aid withdrawal of the tampon and prevent reverse flow from a saturated tampon.
U.S. Pat. No. 4,341,214 (Friese et al.) describes a tampon of a cylinder of hydrophobic foam in a fluid-permeable woven or nonwoven sleeve.
Other patents discuss the shielding of the absorbent tampon core by an occlusive cover. For example, U.S. Pat. Nos. 2,330,257 (Bailey); 4,020,841 (Poncy et al.); and 4,816,100, 4,859,273 and 4,863,450 (Friese) relate to such tampons.
There are several examples in the prior art in which a hydrophilic cover is used as a protective and lubricating interface between the vagina and the highly absorbent core of a tampon. Such a cover is also used to reduce excessive sloughing of fibers from the tampon core to the vaginal wall. Examples of such references are U.S. Pat. Nos. 3,322,123 (Griswold et al.), 4,056,103 (Kaczmarzyk et al.) and 5,006,110 (Alikhan et al.).
Other prior art patents describe blending fibers in the core of the tampon including synthetic, resilient fibers, for improved force and speed of expansion. Examples of such patents are U.S. Pat. Nos. 2,761,449 (Bletzinger) and 4,475,911 (Gellert).
Although many of the tampon structures described above are directed to increasing absorbency and rate of absorbency, not one is concerned with the effect of such increased absorbency on the walls of the vagina. Medical literature reports strong links between standard catamenial tampons and drying lesions in the vaginal epithelium. The reported degree of drying ranges from mild, to moderate causing a wrinkling of the vaginal mucosa, to severe causing layering and peeling, to microulceration, and finally, to frank, gross ulceration. The frequency of occurrence of each level of damage decreases with increasing severity of the damage. One example of this type of study is Raudrant et al., xe2x80x9cStudy of the Vaginal Mucous Membrane following Tampon Utilization: Aspect on Colposcopy, Scanning Electron Microscopy and Transmission Electron Microscopyxe2x80x9d, European J. of O.B. Gyn. and Reprod. Biology, Vol. 31, pp. 53-61 (1989), which reports that high-absorbency tampons can cause drying of the vaginal epithelium, which in turn, may result in abrasions.
It is, therefore, an object of this invention to provide novel tampon products that have a high degree of absorbency, yet do not cause excessive drying of the vaginal epithelium.
The products of this invention aid in preventing drying of the vaginal wall which may come about as a result of tampon use. They accomplish this by substantially minimizing the tampons"" potential to wick moisture from the vaginal wall to the tampon while allowing the tampon""s absorbent core to absorb menstrual or other vaginal secretions. By preventing drying, normal vaginal moisture conditions during tampon wear are maintained.
Clinical studies have shown that vaginal epithelial drying is caused in part by the rapid initial uptake of its natural moisture, as well as the secretions of the vagina and uterus, when a dry, unused tampon is placed in close proximity to the vaginal epithelium. Uptake of vaginal epithelium moisture occurs because of the tendency of the substrates in the system, i.e., the moist vaginal epithelium and the dry, highly absorbent tampon, to equilibrate their relative moisture content. This loss of moisture is due to capillary suction pressure of the absorbent surface as well as the core of the tampon. Increased dryness can cause discomfort, because the vaginal wall may resist withdrawal of the tampon without an appropriate amount of fluid and secretions. This resistance results in an increased likelihood of causing epithelial abrasions.
According to this invention, the reduction of vaginal epithelium drying due to tampon use is accomplished by one or more techniques intended to reduce capillary suction pressure-induced wicking of moisture from the vaginal epithelium by the tampon:
First, a particular kind of outer wrap for the tampon may be used to reduce capillary suction pressure by the tampon. For instance, decreasing the tampon""s capillary suction pressure may be accomplished by decreasing the hydrophilicity of a substantial thickness of the outer portion of the tampon, i.e., by increasing the contact angle with water of the material forming the outer portion of the tampon.
Second, the composition of the absorbent core of the tampon may be adjusted in order to reduce capillary suction pressure. Reducing vaginal wall drying due to tampon use can also be accomplished by decreasing the capillary suction pressure of the core of the tampon by introducing, in substantial amounts, hydrophobic fibers together with hydrophilic fibers in a blend of fibers in the tampon""s absorbent core. The hydrophobic fibers may be made wettable, without reducing their inherent resiliency, by coating them with a surfactant such as polysorbate-20 and the like. Yet another means to reduce the capillary suction pressure of the tampon is to increase the diameter of the fibers in the tampon core to reduce capillary suction pressure or to decrease the density of the tampon core.
The net result of any of these methods is a substantial decrease in the capillary suction pressure of the tampon upon insertion, i.e., when the tampon is unsaturated. One or more of these methods may be used in reducing the drying power of a tampon. Of course, the greater number of methods employed, the lower the risk of drying the vaginal epithelium. For instance, a combination of hydrophobic outer wrap, core fiber blends containing hydrophobic fibers, increased fiber diameter in the core and reduced core density can result in a highly effective tampon having substantially reduced epithelial tissue drying power.